Concrete mixer



w. A. STRONG 3,188,059

CONCRETE MIXER June 8, 1965 4 Sheets-Sheet 1 Filed Feb. 21, 1963 I770 rat/1.53

W. A. STRON G June 8, 1965 CONCRETE MIXER 4 Sheets-Sheet 2 Filed Feb. 21, 1963 'FIGA Jun 8, 1965 w. A. STRONG 3,188,059

CONCRETE MIXER Filed Feb. 21, 1963 4 Sheets-Sheet 3 W. A. STRON G June 8, 1965 CONCRETE MIXER 4 Sheets-Sheet 4 Filed Feb. 21, 1963 United States Patent Ark.

This invention is based upon a discovery which has reduced the mixing time for wet mix concrete and relates to mixing apparatus for this purpose based upon this discovery. The practice of the invention has been found to so increase the work output of a mixer that its bulk can be reduced an amount more than one-half.

Other apparatus for producing wet mix concrete, with which this applicant is familiar, operates by agitation or stirring of the mix, either by bafiles on a rotary drum, or, paddles rotated independently of the drum. In order to obtain the stirring action, speeds are maintained in the range of 6-15 r.p.m. depending on the size of the rotary drum. Speeds are somewhat. higher in the rotary paddle machine, possibly as high as 30 r.p.m. Any higher speeds would merely centrifuge the ingredients without producing any mixing to speak of. It is the mixing speed which determines the size of the apparatus for a given output. There are limitations on the size of portable machines, however, which means that after these limitations are reached, greater output requires more machines. So it happens that it requires the output of several machines to keep a crew of men busy laying the concrete .for building structures, or it requires several trucks to transport the concrete ready mixed, all of which affects the cost chargeable to producing wet mixed concrete.

There are still other advantages to be gained besides a decreased cost by increasing the mixing speed and thereby the output capacity of the mixing apparatus, especially when the apparatus is used to produce lightweight mixes. Aggregates used in such a mix differ. Some, of which expanded mica is an example, absorb waterr Consequently, the longer the mixing cycle, the greater the amount of water required to stay fluid, and, the longer the time for the concrete to set. Lightweight concrete structures require light aggregates of which expanded mica is one, and sintered volcanic ash is another. A mix usually contains any one of these named aggregates or sand with cement and pregenerated air (foam), and this invention is especially adapted to handie such aggregates, because high speed mixing action is obtained.

Lightweight concrete structures also use a foam to trap air in small dispersed pockets. throughout the concrete. The product created by adding foam has not only the advantage of lightweight but it also is a good heat insulator. For example, a mix contains water, foam, sand and cement. The foam for the mix is developed by injecting a liquid detergent, water, and air, all under pressure through a suitable nozzle into the mix of aggregates and cement. The more rapid the mixing action, the better the mix, provided of course, the mixer action is not one which will break the bubbles in the foam. It has been discovered that mixing action can be such as to encourage the development of the foam, and also obtain rapid mixing by the method and apparatus hereinafter described in detail.

One of the objects of this invention is a mixer which mixes by a pumping action of the fluid mix rather than a stirring action; ,1 I I Another object of this, invention is to provide a mixer for concrete whichmixes by a pumping action of the fluid mix to produce turbulence between impinging currents in the fluid'rather than between the pump and the fluid.

. PatentedJune 8, 1965 It is another object of this invention to provide a mixer with a high output capacity for its size.

It is another object of this invention to provide a mixer to produce a wet concrete mix which operates because of pumping action on the fluid rather than stirring action. i

It is another object of this invention to provide a mixer to produce a wet concrete mix which operates on a principle applicable to either batch mixers or continuous delivery mixers.

According to this invention, the mixer has a horizontal mixer casing which is formed by two horizontal rotary pump chambers with open sides. Top and bottom walls connect the open sides forming a connecting chamber between each pump chamber. In each pump chamber is an impeller with a horizontal drive shaft. Spirally formed, or axially inclined blades extend along and are mounted spaced from each shaft. The blades are foraminous in structure and have a solidity ratio within a certain specified range. Each blade is also of uniform radial width and, the relationship between width, solidity ratio and angular speed, produces the desired pumping action later to be described. Opposite ends of the pump chambers are closed and support bearings for the impeller shafts mounted centrally of the ends of the pump chambers. One end of the connecting chamber has a discharge opening closed by a movable discharge gate. The charging opening is located in the top of the connecting chamber and may extend into the adjacent top portions of each pump chamber. Shaft rotational speed varies but depends primarily on the consistency of the mix. An average impeller speed is 50 r.p.m. Water nozzles along the top of each of the pump chambers are directed at the blades of each impeller and connected to a source of water pressure with a water meter,

As pointed out above, there are several variables including the driving speed, all of which must be within certain ranges to obtain the desired mixing. In addition, the mix should fill the chambers to a level above the shaftswhile the impellers are stationary. Anexperienced operator will have no trouble determining the proper amount of mix without stopping the machine.

In carrying out the mixing, the water is turned on first and injected outside the loading zone for the aggregates and cement, then the proper charge of cement and aggregates is added in that order. The operator then watches the meter and the mix. When the proper amount of water has been added, the mix will begin to Fboilj Given the proper pump speed and mixture level, this boiling action will occur when about the right amount of water has been added. What the operator sees at this point, is a wave rising in the connecting chamber, which increases in height as it approaches the discharge end of the mixer. At this .point, maximum mixing action is taking place, and complete mixing will occur in less than half a minute. It is contemplated that this same mixing may be carried outwith distinctly different arrangements of the pumps, such as a cluster of pumps on vertical axes arranged within chambers so as to discharge one into the other.-

Other objects and advantages of this invention will occur to those skilled in the art from the following detailed description, which is in such clear, concise and exact terms as to enable any person skilled in the art to make and usethe same when taken with the illusa trations in the accompanying drawings, forming, apart thereof, and in which:

FIG. 2 is a schematic view in side elevation, illustrating the same machine as shown in FIG. 1;

FIG. 3 is a top plan view of the mixer;

FIG. 4 is a rear elevational view of the mixer;

FIG. 5 is a side elevation in section taken along the line 55 of FIG. 3, looking in the direction of the arrows;

FIG. 6 is a front elevational view taken along the line 66 of FIG. 5; looking in the direction of the arrows;

FIG. 7 is a rear elevational view of the machine showing the addition of a foam nozzle;

FIG. 8 is a view on an enlarged scale showing one blade of an impeller;

FIG. 9 is a fragmentary front elevational view on an enlarged scale showing the discharge gate and its mechanism; and,

FIG. 10 is a view partly in section illustrating a wellknown type of foam nozzle connected to the mixer.

Turning now to the drawings and especially FIGS. 1 and 2 thereof, the mixer generally indicated as 1 is formed by two horizontal pump chambers or casings 3 and 4, with open sides 5 and 6 generally indicated by arrows. Top and bottom walls 7 and 8 connect the open sides 5 and 6 forming a connecting chamber therebetween. In each chamber is an impeller 10 and 11 respectively, on a horizontal drive shaft such as 12 and 13, respectively. Spirally formed axially extending blades 14 are mounted on the impeller 10. Similar blades 15 are mounted on the impeller 11. These blades are foraminous in structure as will be hereinafter described. Opposite ends 17 and 19 of each pump chamber are closed and support bearings such as 20 and 22, shown in FIG. 2, for supporting the opposite ends of shaft 12. A charging opening 24 is provided in the top of the connecting chamber formed by the walls 7 and 8. j

A plurality of water nozzles 26, 28 and 30 are connected to a manifold 32 supplied with water at 34 through a meter 36. Both shafts 12 and 13 are driven at the same speed and in opposite directions. Shaft 12 rotates counter clockwise and shaft 13 clockwise, as viewed in FIG. 1.

As stated heretofore, the practice of the method requires the injection through the nozzles of both pump chambers simultaneously of jets of water directed outside the mixing zone, as shown in FIG. 1. The cement and aggregates are then added through the charging opening 24 in that order. When the proper proportions of aggregate and Water are reached the mixture level with the blades of the impellers stationary would be approximately on the line aa, shown in FIG. 1. Actually, the impellers are not stationary but rotating and consequently, when the proper proportions are reached the mix will appear to boil. The level of the mix then assumes the configuration shown by the dotted line bb' in FIG. 1 and cc' in FIG. 2. Actually, this is a wave with a crest disposed in the connecting chamber. This wave, as viewed in the direction of FIG. 1, would appear to have the shape of the dotted line b-b', the crest of the wave would be at e, and there would be the waterfall portions dd, in each of the pump chambers. As viewed in FIG. 2, the crest of the wave would have the shape cc' due to the spiral or inclination of the blades 14 and 15 of the two impellers. As stated before, it takes less than a half minute to complete the mixing operation after this condition of the mix has been reached. At the end of this time, gate 42 can be opened and the mix will run down the chute 46 until totally discharged.

The reason for the rapid mixing is diagrammatically illustrated in FIG. 1 by a series of arrows, which are placed thereon to indicate the direction of flow and intermixing of currents from the discharge of each of the pump impellers. It will be noted that the mixing is not the result of turbulence created by and around the blades of the impellers, but is due'primarily to the turbulence created in the cross currents discharged from the two impellers which intermix not only in the connecting chamber but also penetrate into the opposite pump chamber. This builds up such a tremendous amount of circulation in the mix as to create the wave shape described. As a consequence, a relatively small machine, such as hereinafter described, with a charge capacity of 12 cubic feet, can have an output as great as 20 cubic yards an hour. This machine, although small, has an output as great as a conventional type of mixer, which will accommodate a 30 cubic foot batch.

The present machine is especially designed to handle aggregates most of which will pass through a one-quarter inch mesh screen. The particular proportions in the composition of the aggregates have some effect on operation, but mixtures including one or more of the following have been used successfully; expanded mica, sintered volcanic ash, sand, and gravel.

Turning now to FIGS. 3 and 4 in the drawings, the mixer 1 has a horizontal mixing chamber 2 formed by two horizontal rotary pump chambers 3 and 4. Each of these pump chambers has an open side 5 and 6 which are joined by top and bottom walls 7 and 8 to form the mixing chamber 2. End walls 17 and 19 close the opposite ends. The top of the mixer casing 1 is provided with a charging opening surrounded by vertical Walls 18. Pref: erably the charging opening is covered by a coarse mesh screen or the like 27. The screen will prevent the ingestion of material of a size which would damage the machine. The bottom wall 8 of the machine is provided with a downwardly inclined chute 9 terminating at a discharge outlet 4!) closed by a movable gate 44. The gate 44 is mounted on the closed end 19 of the mixer casing 1. End wall 19 carries bearings 22 and 23, which have appropriate grease seals to maintain the lubrication for the ends of impeller shafts 12 and 13 respectively. The opposite end wall 17 of the mixer casing carries bearings 20 and 21 which also have grease seals maintaining the lubrication for the opposite ends of impeller shafts 12 and 13 which are journalled therein.

The drive mechanism for the impeller shafts 12 and .13 is best shown in FIGS. 3, 4 and 5. Each of the impeller shafts 12 and 13 carries a drive sprocket such as 51 and 52, respectively. These sprockets are the same size and have the same number of teeth. End wall 17 of the mixer casing carries an adjustable idler sprocket 54 mounted on a bracket 55 welded or otherwise suitably secured to end wall 17. The shaft on which the idler sprocket 54 is journalled is adjustable so as to tension the drive chain 5 7. A loop in drive chain57 is trained around the sprocket 54 and over the sprockets 51 and 52'. A drive sprocket 59 on counter shaft 60 engages a loop in the chain 57 so that each of the sprockets 5 1 and 52 are driven in opposite directions. As viewed in FIG. 4, sprocket 52 rotates counterclockwise and sprocket 51 clockwise. Counter shaht 60 which carries the drive sprocket 59 has fixed thereto a multiple V-belt pulley 62 and the shaft 60 is journalled in suitable pillow blocks 63 and 64 mounted on the base frame members 66 and 67 Spaced from the mixer casing 1 .and also mounted on base frame members 66 and 67 is a motor 70 which drives a multiple V-qbelt pulley 7 .1. A suitable set of V- bel ts 72 drivingly connect the multiple V belt pulleys 7'1 and 62 to drive the impellers on the shafts 12 and 13.

The machine not only has the base frame members 66 and 67 adjacent one end, but also, a further frame member 74 adjacent the opposite end of the mixer casing 1. Suitable sets of brackets, such as 75 and 76 shown in FIG. 4, are mounted on each of the base frame members 66, 67 and 74 and in turn welded to the frame members and the mixer casing 1.

Surrounding the charging opening on three sides is a manifold 32 .with a plurality of branches such as 26, 28 and 30 on the pump casing 3 which discharge water through suitable jets into that pump casing. Pump casing 4 has a plurality of jets 25, 27 and 29, also connected to the manifold 32, which discharge along the pump'casing 4. The location of the jets is such that the pair 25 and 26 discharge more water than the others which have progressively less discharge. In every instance, however, the jets are located outside the center line of shafts 12 and 13 so. that the impellers of the pumps are constantly washed during each revolution. Manifold 32 is supplied with water through a meter 36 connected with a suitable source of water under pressure through the pipe 34. A valve 35 is provided for controlling the correct amount of water .to each load of mix.

The upstanding wall 18 surrounding the charging opening of the mixer casing is provided with a connection 80, shown in FIG. 7, to which may be attached a foam nozzle 81. Liquid detergent is supplied through hose 83 and air through hose 84, both of which are connected with the nozzle 81. Hoses 83 and 84 in turn lead to a supply of liquid detergent and air, both of which are pumped into the nozzle under pressure. The air and detergent are mixed in the nozzle 81, shown in FIG. 10, and a charge of foam delivered through the connection 80 to the charging opening of the mixer. The nozzle 01 is controlled by a suitable valve 8 2,

Bach pump chamber contains an impeller mounting suitable blades. Shaft 12 of one impeller carries three spaced spiders with right angularly arranged legs 10. The ends of these legs mount the blades 14 of the impeller. Impeller shaft 13 likewise carries three spaced spiders having right angularly arranged legs 11 on which are mounted the impeller blades 15. Each spider is nonrotatably secured to its particular shaft, and these spiders on each shaft are slightly staggered one with respect to the other progressively so as to form suitable support for the blades having a total spiral twist in the range of approximately 12. The twist is in a direction to cause the mix to flow toward the discharge opening.

The construction of the blades is more clearly shown in FIG. 8, and, since both impellers are identical, only one will be described. As heretofore mentioned, the shaft 12 of one of the impellers carries a plurality of iders having the spaced van-gularly related legs 10. These spiders have a twist with respect to the shaft 12 so as to support the spiral blades 14. Each impeller is accommodated within a pump casing approximately 48 inches long and 23 /2 inches inside diameter. The impellers are substantially the same length and the same diameter as the pump casings. Each blade 14 is constructed of a sheet 88 of expanded sheet metal which is 13 gauge and has diamond shaped openings by /2 inch. Each sheet is approximately 6 inches Wide and approximately 4 feet long. Each sheet of expanded metal 88 is reinforced along its edges by a frame. Preferably, the frame is composed of one inch longitudinally extending metal strips 89 and 90, either welded or bolted along opposite edges of the expanded metal sheet 88. In the embodiment shown in FIG. 8, the strip 89 clamps a rubber wiper blade 91 between the face of the expanded metal sheet 08 and the frame member 89, Wiper blade 91 is securely clamped by the frame member 89 by bolts spaced at intervals along the frame member 89 and threaded into the expanded metal sheet 88. End frame members 93 and 94 clamp the ends of the expanded metal sheet 88 against the strips 89 and 90, and this assembly is welded to the arms 10 of the spiders. These blades 14 have a void ratio (solids to open) between 10% and 18%. In the modification described, the void ratio is 14%. The rotational speed of the impellers is in the range 50 r.p.m. Although other blade constructions have been tried which range all the way from hardware cloth composed of inch wire screen with /2 inch openings to solid blades, the above-described blade construction and solidity ratio for this particular impeller size, opera-ting at the given range of speed, produces the fastest mixing. In practice, the rubber wiper blade 91 projects approximately /2 inch from the frame member 89. The frame members 89 and 90 are one inch wide strips of metal. Blade 14, therefore, is characterized by having a solid portion. about 1 /2 inches wide along its outer edge and one inch along its inner edge. These solid portions along the outer edge of the blades, or paddles, 14 prevent the paddles 14 from cutting through the material and creating merely local turbulence'instead of the folding action desired by the interaction of currents discharged from each impeller.

FIG. 10 is a schematic illustration of the foam nozzle suitable for connection to the mixer casing wall 18, as shown in FIG. 6. It is believed that the construction 'is well-known in the art and that further explanation is not necessary.

' Turning now to FIG. 9, the discharge opening 40 is controlled by the gate 44, as heretofore mentioned. Gate 44 is guided for vertical movement between a pair of angle iron guide strips 99 and 100 welded along the surface of the end wall .19 of the mixer casing 1 at opposite sides of discharge opening 40. Also welded or otherwise secured to the inner face of each guide strip are a pair of leaf springs 102 and 103. A handle 107 is pivoted at one end on a link 108 and guided in a slotted bracket 109 on end wall 19. Also connected to the handle 107 is a link 110 pivoted both to the handle 107 and to the door or gate 44, as shown in FIG. 9. The handle 107 may be lifted to a position which will maintain the handle 107 and gate 44 raised. Downward pivoted action of the handle 107 forces the gate under the springs 102 and 103 to hold the gate securely over the discharge opening 40.

The operation of the mixer structure will be apparent from its described construction. In mixing a batch, the Water valve 35 is first turned on so that there is a flow from the jets into each pump casing. A charge of cement and then aggregate is added through the charging opening .18 and the jets of water continue until the operator determines from the meter 36 and action in the mixer that the proper charge of water has been added. At this point, the above-described mixing action will take place and be apparent from the turbulence and wave motion in the mix. A-fter less than a half minute, the mix is completed and gate 44 can be opened discharging the mix. The mixer can then be charged with another batch.

If continual mixing is desired rather than by batch, the structure can be modified by extending its length so that batches can be continually added and the discharge be substantially continuous.

Changes in and modification of the construction described may be made without departing from the spirit of my invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In a concrete mixer for producing a wet mix concrete the improvement comprising,

( 1) a pair of round horizontal pump casings with openings along adjacent sides and interconnected at said openings one with the other to form a mixer casing,

(2) a charge receiving opening for said mixer casing,

(3) a pump impeller in each casing having a plurality of blades carrying rubber wipers for contact with the inside of each round pump casing, said blades being spiral lengthwise of the impeller and foraminous,

(4) means to drive said pump impellers in opposite directions,

(5) a discharge opening in said mixer casing,

(6) means to open and close said discharge.

2. In a concrete mixer for producing a wet mix concrete the improvement comprising,

(1) a pair of round horizontal pump casings with openings along adjacent sides interconnected one With the other to form a mixer casing,

(2) a charge receiving opening for said mixer casing,

(3) a pump impeller in each casing,

(4) a plurality of foraminous spiral blades on each pump impeller having a rubber wiper strip at their '7 outer edges for contact with said round pump casings, the total blade area of each impeller being approximately equal to the diameter times the length of each of said round pump casings,

() means to drive said pump impellers in opposite directions but at the same speed,

(6) a discharge opening in said mixer casing,

(7) means to open and close said discharge.

3. In a concrete mixer for producing a wet mix concrete the improvement comprising,

(1) a pair of round horizontal pump casings with openings along adjacent sides interconnected one with the other along the openings to form the mixer casing,

(2) a charge receiving opening for said mixer casing,

( 3) a pump impeller in each casing,

(4) a plurality of foraminous blades on said impellers having a spiral form lengthwise of said pump casings and total blade area on each impeller approximately equal to the diameter of the inside of the pump casing times its length and a void ratio in the range of -18%,

(5) rubber wiper strips along the longitudinal outside edge of each of said blades for contacting the interior of said round pump casings,

(6) means to drive said pump impellers in opposite directions at the same speed,

(7) a discharge opening in said mixer casing, and

(8) means to open and close said discharge.

4. In a concrete mixer for producing a wet mix concrete the improvement comprising,

(1) a pair of round horizontal pump casings with openings along adjacent sides thereof interconnected one with the other to form a closed mixer casing,

(2) a charge receiving opening for said mixer casing,

(3) a pump impeller in each casing,

(4) a plurality of foraminous blades of equal area having a spiral twist of approximately 12 axially of each pump impeller and a combined area in each impeller approximately equal to the internal diameter of the pump casing times its length, the void ratio of each foraminous blade being in the range of from 10-18%,

(5) rubber wiper strips along the outer edge of each 5 blade of each impeller arranged to have a wiping action with the inside of the round pump casings,

(6) means to drive said pump impellers in opposite directions at the same speed,

(7) a disc harge opening in said mixer casing,

(8) a slidable gate for opening and closing said discharge opening.

5. The combination as defined in claim 4 in which said gate is movable along an end wall of said pump casings and provided with cooperating cam shaped springs for wedging said gate to a closed position.

6. In a concrete mixer for producing a wet mix concrete the improvement comprising,

(1) a pair of round horizontal pump casings with openings along adjacent sides and interconnected at said openings one With the other to form a mixer casing, I

(2) a charge receiving opening for said mixer casing,

(3) a pump impeller in each casing having a plurality of blades carrying rubber wipers for contact with the inside of each round pump casing, said blades being spiral lengthwise of the impeller,

(4) means to drive said pump impellers in opposite directions,

(5 a discharge opening in said mixer casing,

(6) means to open and close said discharge.

11/01 Willcox 259--179 11/36 Erickson 259-479 X CHARLES A. WILLMUTH, Primary Examiner. 

1. IN A CONCRETE MIXER FOR PRODUCING A WET MIX CONCRETE THE IMPROVEMENT COMPRISING, (1) A PAIR OF ROUND HORIZONTAL PUMP CASINGS WITH OPENINGS ALONG ADJACENT SIDES AND INTERCONNECTED AT SAID OPENINGS ONE WITH THE OTHER TO FORM A MIXER CASING, (2) A CHARGE RECEIVING OPENING FOR SAID MIXER CASING, (3) A PUMP IMPELLER IN EACH CASING HAVING A PLURALITY OF BLADES CARRYING RUBBER WINGS FOR CONTACT WITH THE INSIDE OF EACH ROUND PUMP CASING, SAID BLADES BEING SPIRAL LENGTHWISE OF THE IMPELLER AND FORAMINOUS, (4) MEANS TO DRIVE SAID PUMP IMPELLERS IN OPPOSITE DIRECTIONS, (5) A DISCHARGE OPENING IN SAID MIXER CASING, (6) MEANS TO OPEN AND CLOSE SAID DISCHARGE. 